selftests/landlock: Add user space tests

mainline inclusion
from mainline-v5.13-rc1
commit e1199815
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6DJU0
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e1199815b47be83346c03e20a3de76f934e4bb34



--------------------------------

Test all Landlock system calls, ptrace hooks semantic and filesystem
access-control with multiple layouts.

Test coverage for security/landlock/ is 93.6% of lines.  The code not
covered only deals with internal kernel errors (e.g. memory allocation)
and race conditions.

Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Reviewed-by: Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210422154123.13086-11-mic@digikod.net


Signed-off-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Yi Yang <yiyang13@huawei.com>